Ionic sensitivity of baroreceptors.
Ionic sensitivity of baroreceptors.
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DOI：
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发表时间：
1987-10
影响因子：
20.1
通讯作者：
Michael C. Andresen;Diana L Kunze
中科院分区：
文献类型：
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作者：
Michael C. Andresen;Diana L Kunze
压力感受器通过产生动作电位对其受体区域的扭曲作出反应，从而向中枢神经系统提供控制心血管的信息。将机械事件转化为电信号的机制尚不清楚。由于不可能记录机械敏感末端的受体电位，研究依赖于对压力感受器末端轴突放电的解释。在本研究中，在控制细胞外液离子组成的研究中，比较了低压和高压受体体外制剂的离子敏感性。这些结果与先前的工作一起表明，钙、钠和钾在各种心血管受体类型中响应的一致性支持共同的机电转导机制。细胞外钠的减少使主动脉弓压力感受器和心房低压压力感受器的阈值升高，压力-放电曲线斜率减小。结果与其他机械感受器的数据一致，认为扭曲激活了通过膜的选择性相对较差的阳离子传导通道。与动脉压力感受器一样，外部钙水平的增加引起心房压力感受器兴奋性的降低。用无机钙通道阻滞剂钴替代一半的外部钙不能改变压力感受器功能。Bay K 8644是二氢吡啶类钙通道阻滞剂中的一种钙通道激动剂，倾向于抑制压力感受器放电，其作用与血管壁内平滑肌激活一致。讨论了几种潜在机制的假设。这些新实验与离子钙改变的结果一致，表明钙进入在压力感受器转导中不起可检测的作用。
Baroreceptors respond to distortion of their receptor regions by producing action potentials and, thus, provide information to the central nervous system for cardiovascular control. The mechanisms converting mechanical events to electrical signals are unknown. Since it has not been possible to record a receptor potential in the mechanosensitive terminals, studies rely on interpretation of axonal discharge of baroreceptor endings. In the present study, the ionic sensitivity of in vitro preparations of both low- and high-pressure receptors are compared in studies in which the ionic composition of the extracellular fluid is controlled. The results taken together with previous work suggest uniformity of response to calcium, sodium, and potassium across a variety of cardiovascular receptor types supporting common mechanoelectrical transduction mechanisms. Decreased extracellular sodium produced increased threshold and decreased slopes of pressure-discharge curves for both aortic arch baroreceptors and for low-pressure baroreceptors in the atrium. Results are consistent with data for other mechanoreceptors where it is believed that distortion activates a relatively poorly selective cation-conducting channel through the membrane. As with arterial baroreceptors, increases in external calcium levels caused a decrease in the excitability of atrial baroreceptors. Substitution of half the external calcium with the inorganic calcium channel blocker cobalt failed to alter baroreceptor function. Bay K 8644, a calcium channel agonist of the dihydropyridine class of calcium channel blockers, tended to inhibit baroreceptor discharge with effects consistent with smooth muscle activation within the vessel wall. Several hypotheses of potential underlying mechanisms are discussed. These new experiments are consistent with the results achieved with alterations of ionic calcium and suggest that calcium entry does not play a detectable role in baroreceptor transduction.